Optical recording medium and its information recording method, and recorder

ABSTRACT

An optical disk includes grooves (G) formed concentrically or spirally from an inner periphery to an output periphery of a disk, wherein prepit ( 1 ) are formed on the lands (L) each sandwiched between grooves and grooves (G). The prepit forming region ( 2 ) is assigned as a region in which a single or a plurality of prepits ( 1 ) are formed. Th prepit forming regions ( 2 ) have a fixed length  36  or less times the recording channel length along the recording track, and are arranged apart from on another by 300 or more times the recording channel bit length along the recording track. On the prepit forming region ( 2 ), a pattern including a long mark or a long space having a length ten or more times the recording channel bit length so that the long mark or long space covers the prepit ( 1 ) on the recording track.

TECHNICAL FIELD

The present invention relates to an optical recording medium, and moreparticularly, to an optical recording medium having grooves formedconcentrically or spirally and prepits formed between and/or on thegrooves. The present invention also relates to an information recordingmethod and a recording unit for recording data on such a high-densityrecording medium.

BACKGROUND ART

Known examples of recordable optical disks include DVD-R (DigitalVersatile Disc-Recordable) and DVD-RW (Digital VersatileDisc-Rewritable). On these recording disks, a recording track is formedwith a fine wobble at a specified frequency (140 kHz). Prepits areprovided on a land, wherein decoding of a signal detected from theprepit can determine the position on the disk.

FIG. 15 shows arrangement of prepits and wobbles provided on a DVD-R orDVD-RW disk. Grooves are used as recording tracks. The groove is formedso as to wobble at a specified frequency when the disk is rotated at aspecified linear speed. For this reason, adjacent recording tracks usemisaligned wobble phases. The recording track on the groove is used fordata recording in units of eight wobbles per frame. For convenience ofthe following description, even-numbered frames are represented by F0and odd-numbered frames are represented by F1. A broken line is used toindicate a boundary between frames. The prepits 15 are formed on theland. In general, the prepit is formed as one or less pit per one cycleof the wobble on a land adjacent to the outer periphery side of frame F0on a groove. One succeeding prepit may overlap with another prepitformed on the inner periphery of frame F0. In this case, the succeedingprepit is formed on a land adjacent to the outer periphery of frame F1instead of frame F0. In either case, prepits are formed in first threewobbles of a frame where the recording track has a specified wobblephase.

FIG. 16 shows a format for recording and reproduction. One frameincludes therein a 2-byte synchronization pattern (SY) and 91-byte data.Since one byte includes 16 channel bits, one wobble has a cycle of 186channel bits. The prepits appear at a cycle of 186 channel bits in thecase of the shortest interval.

It is known that a high recording density can be realized by using boththe land and the groove as recording tracks. This is because ofpreventing an influence by interference between codes due to data onadjacent tracks. It is possible to create a disk having the same trackdensity by doubling the groove cycle compared to a disk using only thegroove as a recording track. This technique is effective for realizinglarge-capacity disks.

In order to use both the land and the groove on a disk, it is necessaryto form physical address information identifiable from both the land andthe groove so as not to unfavorably affect reproduction of data on therecording track. When both the land and the groove are used as recordingtracks on the above-described DVD-R and DVD-RW disks, data recorded onthe land is strongly interfered by prepits also recorded on the land.Thus, correct data reproduction has been difficult.

Grooves are formed on DVD-R and DVD-RW disks so that the wobblefrequency of the grooves becomes constant on the entire disk surface.Such disks are subject to gradual misalignment between phases of groovesadjacent to both sides of a land. Consequently, a correct frequencycannot be detected from the recording track on the land.

The wobble arrangement as described in Patent PublicationJP-A-2001-250239 can be used to solve the above problem that a correctwobble frequency cannot be detected on the land. JP-A-2001-250239exemplifies the wobble arrangement such as shown in FIG. 17 so as toavoid interference due to misalignment of wobble phases betweenrecording tracks on the grooves. FIG. 17 shows a partly enlarged zone onan optical recording medium. As shown in FIG. 18, zones areconcentrically arranged on an optical recording medium 3. The zones areso formed as to be divided into zone 1 along the innermost periphery tozone N (N is an integer) along the outermost periphery. FIG. 17 shows anexample of keeping a constant wobble phase between adjacent tracks ineach of the divided zones. This makes it possible to align wobble phasesof the adjacent grooves and prevent interference due to the wobblebetween recording tracks.

Forming groove phases in this manner is also effective for using landsand grooves as recording tracks. Maintaining the constant land widthmakes it possible to correctly detect a wobble frequency on lands aswell as on grooves. Even though wobble phases are aligned on theadjacent tracks, however, it is impossible to solve the first problem ofinterference between a prepit and data on the recording track. Prepitspartially enter the data region on a recording format similar to thoseused for DVD-R and DVD-RW. Interference from prepits frequently causesdata read errors.

On the other hand, there is a method of supplying address information tothe recording track in such a manner as to frequency modulate the wobbleon CD-R or CD-RW. In this case, the physical address information isrecorded on the disk without using prepits to decrease deterioration ofthe reproduced signal quality due to interference from the physicaladdress information. However, it is difficult to modulate the wobble soas to correctly detect the address information from both the land andthe groove. Thus, it is considered that both the land and the groovecannot be used as recording tracks.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an optical recordingmedium having address information detectable from both a land and agroove without adversely affecting recording data when both the land andthe groove are used as recording tracks, and information recordingmethod and recording unit thereof.

It is to be noted that the present invention relates to a prepitarrangement for using both the land and the groove as recording tracks.This makes it possible to record the address information in a commonformat between an optical recording medium using both the land and thegroove as recording tracks and a medium using either the land or thegroove as a recording track, thereby allowing a common recording methodto be used therebetween. This common method aims at using a commoncircuit concerning address identification and format management by therecording unit to ensure high compatibility between both the media. Forthis reason, the optical recording medium using only the land or thegroove also requires arrangement of the address information compliantwith the prepit arrangement on the optical recording medium using boththe land and the groove.

The present invention provides, in a first aspect thereof, an opticalrecording medium including: grooves concentrically or spirally arrangedfrom a radially inner periphery toward a radially outer periphery of themedium, lands each disposed between two of the grooves adjacent to eachother in a radial direction of the medium, recording tracks eachdisposed in the groove and/or the land, and a plurality of prepitforming regions disposed in the groove and/or the land and each capableof receiving therein a single or plurality of prepits:

the plurality of prepit forming regions are disposed apart from oneanother by a distance which is 300 or more times a recording channel bitlength:

each of the prepit forming regions having a fixed length which is 36 orless times the recording channel bit length along the groove or land.

The present invention provides, in a second aspect thereof, a method forrecording data on the optical recording medium according to the presentinvention as described above, the method including the step of recordinga pattern including a long mark or a long space having ten or more timesthe channel bit length so that the prepit on the recording track iscovered with the long mark or long space on the prepit forming region.

The present invention provides, in a third aspect thereof, a recordingunit for recording data on the optical recording medium according to thepresent invention as described above, the recording unit including: aprepit detecting section for detecting a prepit signal from a signalreproduced from the optical recording medium; a decoding section fordecoding the prepit signal to output physical address information; arecording pattern generating section for admixing, based on data to berecorded, a recording pattern including a long mark or a long spacehaving a length ten or more times the channel bit length to the data tobe recorded, to generate physical address information; and a recordingtiming control section for detecting a recorded position based on thephysical address information, and controlling timing for start of arecording pattern output from the recording pattern generating sectionand a channel bit frequency, wherein the recording timing controlsection controls output timing of the recording pattern so that the longmark or the long space output from the recording pattern generatingsection covers the prepit.

When the land and the groove are both used as recording tracks, therecording medium and the recording method according to the presentinvention can correctly detect wobble phases on the land and the grooveand form prepits as information containing physical addresses detectablefrom the land and the groove.

The use of the recording method and the recording unit according to thepresent invention can protect a prepit forming region with a long markor a long space. Even a recorded medium enables correct reading ofinformation from a prepit. In addition, it is possible to preventinterference with a reproduced signal from a prepit and prevent a readerror from occurring. These effects enable provision of the opticalrecording medium, the recording method, and the recording unit (orrecording/reproducing unit) capable of high-density recording.

As described in preferred embodiments of the present invention, the longspace or the long mark can be selected depending on a frame to berecorded. When a multi-layer medium is used, there is provided an effectof avoiding occurrence of an inter-layer crosstalk resulting fromlocally concentrating long marks or long spaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing the arrangement of prepits and wobbleson an optical recording medium according to a first embodiment of thepresent invention;

FIG. 2 is a top plan view showing the arrangement of prepits and wobblesat zone boundaries on the optical recording medium according to thefirst embodiment;

FIG. 3 is a timing chart exemplifying prepits and wobble waveformsdetected on a groove and a land of the optical recording mediumaccording to the first embodiment;

FIG. 4 is a diagram exemplifying a prepit recording format;

FIG. 5 is a block diagram showing a recording unit/reproducer having theoptical recording medium according to the first embodiment;

FIG. 6 is a diagram exemplifying a data format;

FIG. 7 is a table exemplifying modulated codes;

FIG. 8 is a table exemplifying synchronization patterns;

FIG. 9 is a top plan view showing the arrangement of prepits and wobbleson an optical recording medium according to a second embodiment of thepresent invention;

FIG. 10 is a top plan view showing the arrangement of prepits andwobbles on an optical recording medium according to a third embodimentof the present invention;

FIG. 11 is a timing chart exemplifying prepits and wobble waveformsdetected on a groove and a land of the optical recording mediumaccording to the third embodiment;

FIG. 12 is a top plan view showing the arrangement of prepits andwobbles on an optical recording medium according to a fourth embodimentof the present invention;

FIG. 13 is a timing chart exemplifying prepits and wobble waveformsdetected on a groove and a land of the optical recording mediumaccording to the fourth embodiment;

FIG. 14 is a view showing the arrangement of prepits on an opticalrecording medium according to a fifth embodiment of the presentinvention;

FIG. 15 is a top plan view showing the arrangement of prepits andwobbles on a conventional optical recording medium;

FIG. 16 is a diagram exemplifying a conventional data format;

FIG. 17 is a top plan view showing second arrangement of prepits andwobbles on a conventional optical recording medium; and

FIG. 18 is a top plan view showing arrangement of zones on an opticaldisk.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in further detailwith reference to the accompanying drawings so as to ascertain theforegoing and other objects, features, and advantages of the presentinvention.

FIG. 1 shows the arrangement of prepits and wobbles formed on an opticalrecording medium according to a first embodiment of the presentinvention. Grooves (G) are continuously and spirally formed from theinner periphery to the outer periphery of the disk. The grooves areformed while wobbling at an approximately constant frequency in a radialdirection. The grooves disposed adjacent to one another in each zonehave the same phase. FIG. 1 is a partially enlarged view of the samezone on the disk formed in this manner. In each zone, the lands (L) eachsandwiched between grooves are formed to have a constant track width.For this reason, the following advantages are available. That is, evenwhen the groove and the land are used as recording tracks, an excellentwobble waveform can be detected on both. Reproduced waveforms are hardlysubject to an amplitude variation caused by a variation in the recordingtrack width.

On the groove, frames F1, F2, F3, and F4 are periodically arranged alongthe track in this order. Each zone is configured so that the number offrames per recording track is set to 4K+1 (where K is an integer).Frames F1, F2, F3, and F4 have a length equivalent to an integralmultiple of the wobble frequency and are aligned with one another alongthe radial direction. A prepit forming region 2, which is shown shadedin the drawing, starts at the beginning of frame F1 on the groove andapart from the frame boundary along the recording track by twelve timesthe channel bit length T. The prepit forming region 2 is twelve times aslong as the channel bit length T. The prepit forming region 2 is so wideas to cover three recording tracks including the groove and bothadjacent lands. A prepit 1 is provided inside the prepit forming region.The prepit 1 is formed in such a manner that both walls of the grooveare shifted approximately half the recording track toward the outerperiphery side. Such prepits can be formed by using an exposure beam forprepit formation in addition to a beam for groove exposure during theexposure of a master disk. The exposure beam for prepit formation isradiated at a position shifted approximately half a track toward theouter periphery. That is, the prepit 1 is formed by decreasing theradiation amount of beam for groove exposure at the prepit formationposition and by radiating the prepit formation beam toward the outerperiphery side. If a prepit is formed to have a length which is fourtimes the channel bit length along the recording track, differentpatterns can be formed depending on positions corresponding to prepitsin the prepit forming region that is divided into three portions. Theinformation including physical addresses is represented by patterns offorming prepits in a plurality of prepit forming regions arranged alongthe recording track.

A land is assigned with a frame number corresponding to a groove that isadjacent to the land in the direction of the outer periphery side.According to this frame arrangement, the land's frame F1 adjoins theinner periphery side of the groove's frame F1, whereas the land's frameF2 adjoins the outer periphery side of the groove's frame F1. On thegroove, any prepit forming region is positioned near the beginning offrame F1. On the land, any prepit forming region is positioned near thebeginnings of frames F1 and F2. Along the track direction, the shortestinterval of prepit forming regions is measured between the prepitforming region on the land's frame F1 and that on the land's frame F2.Thus, the interval is ensured to be almost equal to the frame length.

An operation to record data on the disk uses a recording format havingsynchronization patterns including a long mark and a long space in eachframe so that the long mark or the long space covers the prepit formingregion on the recording track. For this reason, the length of the prepitforming region significantly influences the efficiency of the recordingformat. The prepit forming region needs to have a minimum length enoughto form at most several prepits inside the same. In addition, the cycleof prepit forming regions must be ensured wide enough for thesynchronization pattern length. The purpose thereof is to prevent theefficiency of data regions from degrading even when a synchronizationpattern including the long mark or the long space is formed on theprepit forming region. In the prepit forming region, it is impossible tocorrectly obtain signals for the servo circuit used for positioningcontrol of the focusing beam of the optical head. If a prepit formingregion is made unnecessarily long, it disorders the positioning controlto adversely affect the recording and reproducing performance. Inconsideration for this, it is necessary to configure the prepit formingregion as short as possible and ensure a sufficient interval betweenthem.

At least, the length of the prepit forming region is configured 36channel bits or less equivalent to the three-byte length according tothe (1,7) run-length limited coding. The prepit forming regions arearranged at an interval of 300 channel bits or more equivalent toapproximately ten times the length of the prepit forming region. Thismakes it possible to protect the format efficiency against the presenceof prepits. Further, it is possible to prevent prepits from adverselyaffecting signals for the servo circuit to realize optical diskssuitable for high-density recording.

When the prepit forming region is ensured to be longer than 36 channelbits, it is necessary to use a synchronization pattern of four bytes orlonger so as to stably form a long mark or a long space on the prepitforming region. Thus, a problem may arise in that addition of thesynchronization pattern decreases the format efficiency. It isappropriate to determine the length of the prepit forming region to beup to 36 channel bits equivalent to three bytes. The prepit formingregions may be arranged at an interval of 300 channel bits or moreequivalent to approximately ten times the prepit forming region length.This can limit the region of disordering signals for the servo circuitto approximately 10% or less of the entire region. It is desirable toarrange the prepit forming regions at an interval of 300 channel bits ormore to prevent the servo characteristics from degrading and ensure theaccuracy of the positioning control of the focusing beam by the opticalhead.

FIG. 2 shows a partially enlarged figure of a zone boundary. In eachzone, wobble phases are aligned and frames are arranged in order.Accordingly, frame boundaries are aligned along the radial direction ineach zone. On the contrary, wobble phases and frame boundaries aremisaligned across the zone boundary. The example depicted in FIG. 2shows that wobble phases and frame boundaries are misaligned, when azone boundary exists on the land and wobble cycles are changed stepwiseacross the zone boundary. Since wobble cycles change across the zoneboundary, it is difficult to accurately identify a channel clock. On thezone boundary, prepit forming regions appear irregularly to the innerperiphery side and the outer periphery side. It is thus difficult toavoid crosstalk caused by prepits in the recording. For this reason, itis desirable not to use several tracks for data recording orreproduction near the zone boundary.

FIG. 3 exemplifies waveforms obtained from wobbles and prepits on theoptical recording medium according to the first embodiment. Therecording track on the groove shows a prepit only at the beginning ofthe frame F1. A reproduced waveform from the prepit is obtained as apulse superposed on the wobble. Assuming that the wobble cycle is 24times the channel bit length, the information including physicaladdresses can be demodulated based on the relationship between theprepit detection timing and the wobble phase. It is also assumed herethat the prepit forming region is divided into three sections eachhaving a length of 4T and that the presence or absence of prepit isrepresented as 1 or 0 in each section. When four types of patterns 101,100, 010, and 001 are used, it is possible to represent one-bitinformation and a code boundary per four frames. At the beginning of thecode, for example, patterns 100 and 101 are allocated to data “0” and“11”, respectively. Otherwise, patterns 010 and 001 are allocated todata “0” and “1”, respectively.

On the land, a prepit detection pulse is obtained at the beginning offrame F1 because the boundary is deformed between the land and thegroove adjacent thereto in the direction of the outer periphery side. Inaddition, a prepit is also detected at the beginning of frame F2 becausethe boundary is deformed between the land and the groove adjacent to theinner periphery side. No prepit appears in frames F3 and F4. A prepitcan be selected for detection only from frame F1 even on the land byusing the frame cycle and the fact that no prepit is detected from thepreceding frames. In this case, when the physical address information isobtained from the prepit on the land, that information becomes identicalto the physical address information on the groove adjacent thereto inthe direction of the outer periphery side. A tracking polarity is usedto make a distinction between physical addresses for the land and thegroove.

FIG. 4 exemplifies a format to record information including a physicaladdress supplied to a prepit. Since one bit of prepit information issupplied per four frames, 52 bits obtained from 208 frames configurescode information. The code information contains a 24-bit physicaladdress, 8-bit additional information, and a 20-bit (5-symbol) ECCparity. The ECC parity is provided to correct a prepit detection errorthat is divided into five 4-bit symbols. The provision of the ECC paritycan correct up to two symbols of a prepit detection error and detectthree symbols of a detection error.

The following describes the recording and reproducing method using theoptical recording medium according to the first embodiment of thepresent invention. FIG. 5 exemplifies the configuration of arecording/reproducing unit during recording and reproducing while usingthe optical recording medium according to the first embodiment. A servocircuit (not shown) controls positions of an optical head 4. The opticalhead 4 focuses a light beam onto a recording track disposed on theoptical recording medium 3 and outputs, from the recording track, thewaveform as shown in FIG. 3 that the pulse waveform resulting from theprepit is superposed on the wobble waveform, as a difference signal froma detector (not shown) that is bisected in the direction along thetrack. In addition, the above-described bisected detector generates asum signal representing a contrast change resulting from recording pitsformed on the recording track. A binary-coding circuit provided in aprepit detection circuit 5 detects the timing of the presence of theprepit to generate a prepit detection pulse. The binary-coding circuitalso receives the wobble waveform superposed on a pulse waveform, tooutput a binary signal synchronized with the wobble.

A prepit decoding circuit 7 decodes information containing a physicaladdress, which is provided to the prepit, based on the prepit detectionpulse timing and the number of pulses obtained by the prepit detectioncircuit and based on the timing of the binary signal of the wobbleobtained by the wobble detection circuit, outputting the same. Data isrecorded on the optical recording medium as follows. First, a hostsystem (not shown) stores data to be recorded in a data buffer 13. Then,the host system (not shown) specifies a logical address of the data tobe recorded to the recording/reproducing control circuit. Therecording/reproducing control circuit encodes the data to be recordedbased on the specified logical address and performs error correctioncoding. The recording/reproducing control circuit also calculates aphysical address of the data to be recorded based on the logical addressand outputs the physical address to the timing control circuit 11. Thetiming control circuit is supplied with the prepit detection pulsetiming from the prepit detection circuit and the binary signal of thewobble from the wobble detection circuit 6. Based on the input pulsetiming and binary signal, the timing control circuit synthesizes arecording clock synchronized with a rotational speed of the opticalrecording medium 3. The timing control circuit uses the physical addressinformation output from the prepit decoding circuit 7, to detect thestart position of the physical address for the data to be recorded. Whenidentifying the physical address of the data to be recorded and suppliedfrom the recording/reproducing control circuit, the timing controlcircuit outputs the recording clock and a recording gate signal to theformat control circuit 10. The format control circuit adds asynchronization pattern to the data received from therecording/reproducing control circuit and applies coding modulation tothe data. The format control circuit outputs a recording control pulseto an LD drive circuit 9 in synchrony with the recording clock. Theoptical head 4 then forms a recording pit on the optical recordingmedium 3.

The timing control circuit detects a phase difference between twotimings. One is output timing of a pattern equivalent to the long markor the long space determined by the recording clock frequency. The otheris the timing for the wobble phase or the prepit detection pulse.Continuously providing the frequency control using a phasesynchronization loop makes it possible to continue recording so as toform the long mark or the long space on prepits at any time.

Data is reproduced as follows. The optical head 4 reads the signalrepresenting the contrast change from the optical recording medium.Based on this signal, a data determination circuit determines binarydata. The format control circuit extracts the synchronization anddecodes the data. The host system (not shown) specifies the logicaladdress of data to be reproduced for the recording/reproducing controlcircuit. Based on this logical address, the recording/reproducingcontrol circuit calculates a physical address and outputs the same tothe timing control circuit. The format control circuit specifies thestart timing of the reproduced data for the format control circuit basedon the physical address obtained from the prepit decoding circuit and asynchronization extraction result from the binary data. The formatcontrol circuit extracts the specified timing data and outputs the sameto the recording/reproducing control circuit. The recording/reproducingcontrol circuit applies error correction to the input data, stores thereproduced data in the data buffer, and notifies completion of the datareading to the host system (not shown).

The following describes in more detail the physical format used forrecording and reproduction. During recording, the format control circuitadds a synchronization pattern in the format as shown in FIG. 6. Oneframe includes a 3-byte synchronization pattern SY and 91-byte datacontaining an error correction parity added by the recording/reproducingcontrol circuit. If the coding modulation provided by the format controlcircuit uses the NRZI recording based on the (1,7) run-length limitedcoding at a coding ratio of 2/3 as shown in FIG. 7, one byte equals 12channel bits and one frame equals 1128 channel bits, thereby having anintegral multiple of 24 channel bits of the wobble frequency. The formatcontrol circuit contains a (1,7) modulation circuit (not shown) that hastwo states S0 and S1. The initial state is S0. An internal state, inputdata, and a succeeding state determine a modulated code to be output andthe next state. In the coding table of FIG. 7, the symbol X may denoteeither “0” or “1”. The symbol R denotes using an inverted version of abit immediately before the modulated code. Particularly when the currentstate is S0 and the input data is 10, the modulated code R00 is outputto set the next internal state to S1 even when the synchronizationpattern (SY) follows.

The synchronization pattern SY can be any of patterns each including 36channel bits as shown in FIG. 8, for example. The synchronizationpattern is also selected depending on the internal state of the (1,7)modulation circuit. After the synchronization pattern is output, thenext internal state is changed to S0 at any time. In the table of FIG.8, the symbol R denotes using an inverted version of a bit in theimmediately preceding modulated code. The symbol Y is optional for thepurpose of controlling direct current components in therecording/reproduced signal. The table in FIG. 8 provides two types ofsynchronization patterns for each of states S0 and S1. When the NRZIrecording is performed, one of the two types of synchronization patternscontains a mark of 24 channel bit length at the center. The otherpattern contains a space of 24 channel bit length. Either of twopatterns can be selected independently of input data.

In the case of using an optical recording medium according to the firstembodiment of the present invention, the prepit forming region begins atthe end of 12 channel bits after the frame boundary and has a length of12 channel bits. Now, it is assumed here to select a pattern containinga space of 24 channel bit length from the synchronization patterns shownin FIG. 8 and to perform the recording so that the beginning of thesynchronization pattern starts from the frame boundary. In this case,the prepit forming region can be contained in the space of 24 channelbit length at any time. There may be a case of using a medium that issubject to degradation in the reflectance by forming a mark. In such acase, it is possible to avoid a decrease in the prepit detection ratioon a recorded disk because the prepit is protected within the long spaceat any time. The DVD-R and DVD-RW formats allow prepits to exist outsidethe synchronization pattern. A prepit disorders the reproduced waveform,causing an error during data reproduction. By contrast, the opticalrecording medium and the recording unit according to the embodimentrestrict prepits to exist only inside the long space in thesynchronization pattern, thereby significantly reducing the adverseeffect on data reproduction.

The prepit forming regions exist only on frames F1 and F2. Frames F1 andF2 may be used to select synchronization patterns containing longspaces. Frames F3 and F4 may be used to select synchronization patternscontaining long marks. Since the long mark and the long space are mixedin this manner, it is possible to decrease a crosstalk from adjacentrecording layers due to changes in the reflectance or the transmittanceeven on a medium having multiple recording layers, for example.

The above-described embodiment has presented the example of using the(1,7) run-length limited coding for modulation and configuring the framewith the 3-byte synchronization pattern and the 91-byte data. Themodulation code and the frame configuration are not limited thereto andcan be selected in accordance with system requirements. For example, itis also possible to use the same 8/16 modulation as used for DVD-R andDVD-RW and use a 2-byte synchronization pattern containing a mark or aspace of 14 channel bit length. In addition, any wobble frequencies canbe selected except the limitation that a common wobble phase is providedto the recording tracks adjacent to one another in each zone. Theembodiment has presented the example where the frame length is anintegral multiple of the wobble frequency. For example, four frames mayinclude an integral multiple of wobbles. In this case, no error occursin the prepit decoding because the F1 frame ensures the relativerelationship between the wobble phase and the prepit position.

FIG. 9 exemplifies arrangement of prepits and wobbles formed on anoptical recording medium according to a second embodiment of the presentinvention. The embodiment presents an example of deforming only a sidewall at the groove's outer periphery side as another example of formingprepits by deforming a groove side wall. Such prepits can be formedduring exposure on a master disk by radiating a groove exposure beam anda prepit formation exposure beam only at the position for forming aprepit. The prepit formation exposure beam is radiated to a positiondeviated approximately half a track toward the outer periphery. When aprepit is formed by deforming the side wall only at the outer peripheryside, a prepit forming region exists on a land and a groove sandwichingtherebetween the deformed side wall. Frame F2 on the groove or frame F4on the land is not influenced by deformation of the side wall and has noprepit forming region. Data formatted as shown in FIG. 6 can be recordedon the optical recording medium where prepits are formed as shown inFIG. 9.

Forming prepits as described above decreases the size of a reproducedwaveform from a prepit obtained on the groove compared to thedeformation of groove's both walls as shown in FIG. 1. A prepit formingregion can be formed as wide as one track on the land and the groove,thereby increasing the design choice of the formats. FIG. 9 shows theexample of providing the prepit forming region at a cycle of fourframes. In this case, there occurs no interference between adjacentprepit forming regions by selecting the number of frames per track sothat it differs from a multiple of the cycle of prepit forming region.For example, prepit forming regions can be arranged so as not to adjointo one another when the number of frames per track is determined to be3K+1 (K is an integer) and a prepit forming region is provided everythird frame. Alternatively, the number of frames per track is determinedto be 5K+2 (K is an integer). Frames are numbered as F1, F2, F3, F4, andF5 in units of five frames. Of these frames, prepit forming regions canbe provided only on frames F1 and F2. Also in this case, prepit formingregions can be arranged so as not to adjoin to one another. In thismanner, it is possible to prevent the long space or the long markrecorded on the prepit forming region from being concentrated on therecording/reproducing beam of the optical head. There is provided aneffect of hardly generating an inter-layer crosstalk even on a mediumhaving multiple recording layers.

FIG. 10 exemplifies arrangement of prepits and wobbles formed on anoptical recording medium according to a third embodiment of the presentinvention. The example shows formation of prepits by disconnecting thegroove. When prepits are formed by disconnecting the groove in thismanner, only a groove formation exposure beam can be used to expose amaster disk. However, different prepit detection methods must be usedfor a recording track on the land and a recording track on the groove.FIG. 11 exemplifies waveforms of a sum signal and a difference signalobtained from a bisected detector of the optical head. A recording trackon the groove causes a pulse waveform resulting from a prepit to besuperposed on the sum signal at the beginning of frame F1 containing thegroove disconnection. On the other hand, a wobble waveform appears inthe difference signal on which, however, a pulse waveform resulting froma prepit is not superposed. When a mark is formed on the recordingmedium, the sum signal shows a contrast change as indicated by a shadedportion. There may be a case of recording a synchronization patternregularly containing the long space on a prepit forming region. In thiscase, the prepit forming region is not affected by a decrease in theamount of reflected light due to the mark. A prepit detection pulse canbe easily obtained simply by supplying the prepit detection circuit witha sum signal output from the optical head and binary-coding the signalaccording to the amount of reflected light. A recording track on theland causes a pulse waveform resulting from a prepit to be superposed onthe difference signal. The pulses have reverse polarities between frameF1 and frame F2. If the prepit detection circuit correctly configures aslice level, the pulse output is only available from frame F1.

FIG. 12 exemplifies arrangement of prepits and wobbles formed on anoptical recording medium according to a fourth embodiment of the presentinvention. A prepit is formed as an emboss pit in a prepit formingregion on the land. FIG. 13 exemplifies waveforms of a sum signal and adifference signal obtained from the bisected detector of the opticalhead. Also in this case, different prepit detection methods are used fora recording track on the land and a recording track on the groovesimilarly to reproduced waveforms from the optical recording mediumaccording to the third embodiment. A recording track on the groovecauses a pulse waveform resulting from a prepit on the adjacent land tobe superposed on the difference signal from the bisected detector of theoptical head in frames F1 and F2. The pulses have different polaritiesbetween frame F1 and frame F2. If the prepit detection circuit correctlyconfigures a slice level, the pulse output can be obtained solely fromframe F1. A recording track on the land causes a pulse waveformresulting from a prepit to be superposed on the sum signal similarly tothe recording track on the groove of the optical recording mediumaccording to the third embodiment. Also in this case, it is possible toavoid a prepit detection error due to interference with a recording markby recording the long mark and the long space in the prepit formingregion.

The above-described embodiments have presented the examples of coveringthe prepit forming region with the long space. However, for example,there may be a case of using a medium that increases a reflectance byforming a mark. In such a case, it may be preferable to regularly coverthe prepit forming region with the long mark. It may be optional torecord the long mark or the long space on the prepit forming region. Thelong mark or the long space need not necessarily be contained in asynchronization pattern on a frame where no prepit forming region isavailable.

The above-described embodiments have presented only the examples offorming one or more prepits within the prepit forming region. Further,it is possible to include a pattern for forming no prepit among thepatterns each for forming a prepit in the prepit forming region. Forexample, it is possible to form one or zero prepit in a single prepitforming region and configure the address information to represent thepresence or absence of the prepit. This case also enables a physicaladdress to be decoded based on the continuity thereof. Moreover, addingan odd parity to the prepit at a proper cycle can further reduce thetime length to establish the synchronization.

It is a principal object of the present invention to provide an opticalrecording medium having address information detectable from both a landand a groove without adversely affecting the recording data when boththe land and the groove are used as recording tracks. Further, similarprepit arrangement and recording method can be applied to an opticalrecording medium using only the groove or the land as a recording track.

FIG. 14 exemplifies prepit arrangement formed on an optical recordingmedium according to a fifth embodiment of the present invention. Thisexample uses only the groove as a recording track and provides a prepitas disconnection of the groove. Frames have a boundary as indicated by abroken line and are formed by dividing a recording track provided on thespirally arranged grooves into equal lengths. The frames are not alignedin the radial direction. The grooves may wobble at a specifiedfrequency. FIG. 14 shows the example of using the unwobbled groove.Prepit forming regions are provided only on frames F1 and F2 out ofnumbered frames F1, F2, F3, and F4 in a cycle of four frames along therecording track. In this case, the prepit detection timing becomes thesame as that obtained on the land according to the prepit arrangementdescribed according to the first embodiment of the present invention.Therefore, it is possible to use the same format as shown in FIG. 6.

The example in FIG. 14 uses the recording track having no wobble formed.In this case, the prepit information cannot be decoded based on therelative relationship between the wobble phase and the prepit position.However, the prepit information can be identified by using theperiodicity of the prepit forming region, a relative position of aprepit succeeding to frame F1 or frame F2, and a prepit formationpattern. For example, the prepit information can be easily detected byemploying a method of limiting the prepit formation pattern to 100 or101 for the prepit forming region in frame F1.

While there has been described the present invention based on thepreferred embodiments, the optical recording medium, and the informationrecording method and recording unit according to the present inventionare not limited to the above-described embodiments. The scope of thepresent invention also includes various changes and modifications madeto the above-described embodiments.

Industrial Applicability

The optical recording medium according to the present invention can beparticularly suitably applied to DVD-R and DVD-RW capable of recordingon both the land and the groove.

1. An optical recording medium comprising: a plurality of groovesconcentrically or spirally arranged from a radially inner peripherytoward a radially outer periphery of the medium, a plurality lands eachdisposed between two of said grooves adjacent to each other in a radialdirection of the medium, a plurality of recording tracks each disposedin said groove and/or said land, and a plurality of prepit formingregions disposed in said groove and/or said land and each capable ofreceiving therein a single or a plurality of prepits: said plurality ofprepit forming regions are disposed apart from one another by a distancewhich is 300 or more times a recording channel bit length: each of saidprepit forming regions having a fixed length which is 36 or less timessaid recording channel bit length along said groove or land, said prepitforming regions having a fixed length which is three or less tracks longalong said radial direction and being disposed not adjacent to oneanother in said radial direction.
 2. The optical recording mediumaccording to claim 1, wherein said recording track and said prepitforming region are disposed in each of said groove and said land.
 3. Theoptical recording medium according to claim 1, wherein said mediumincludes a plurality of zones divided in said radial direction, and saidprepit forming regions in each of said zones are arranged, in alignmentwith one another in said radial direction, at a cycle corresponding to aspecified number of recording tracks, along a plurality of lines whichdivide said medium by an integer in a circumferential direction of saidmedium.
 4. The optical recording medium according to any one of claim 1,wherein said medium includes said plurality of zones divided in saidradial direction, and said wobbles are in-phase with one another.
 5. Theoptical recording medium according to any one of claim 1, wherein saidprepits in said prepit forming region are formed by deforming grooveside walls.
 6. The optical recording medium according to any one ofclaim 1, wherein said prepits in said prepit forming region are formedby disconnection of said grooves.
 7. The optical recording mediumaccording to any one of claim 1, wherein said prepit in said prepitforming region is formed as an emboss provided on said land.
 8. Theoptical recording medium according to any one of claim 1, wherein saidprepit forming region is provided, in number of one at most for eachframe forming a unit of data arranged on said recording track, at aspecified position of said each frame
 9. The optical recording mediumaccording to claim 8, wherein the number of frames per said recordingtrack is an integer, and said prepit forming regions are intermittentlydisposed in said frames so that one of two of said recording tracksformed on respective said lands sandwiching therebetween one of saidgrooves, or formed on respective said grooves sandwiching therebetweenone of said lands, includes therein said prepit forming region in one ofsaid frames, whereas the other of said two of said recording tracksincludes therein no prepit forming region in said one of said frames.10. The optical recording medium according to claim 8, wherein saidrecording track has a wobble cycle equal to 1/n of a frame cycle. 11.The optical recording is according to claim 1, wherein a prepit arrayincluding at least one prepit and formed in said prepit forming regionis recorded so as to provide part of physical address information orsubsidiary information of said medium.
 12. The optical recording mediumaccording to claim 4, wherein a single prepit is formed in each saidprepit forming region, and is recorded so as to provide part of physicaladdress information or subsidiary information of said medium based on arelative relationship between the wobble phase and the prepit position.13. A method for recording data on the optical recording mediumaccording to claim 1, said method comprising the step of recording apattern including a long mark or a long space having ten or more timessaid channel bit length so that said prepit on said recording track iscovered with said long mark or long space on said prepit forming region.14. A method for recording data on the optical recording mediumaccording to claim 1, said method comprising the step of recording apattern including a long mark or a long space having ten or more timessaid channel bit length so that said prepit on one of said recordingtracks is covered with said long mark or long space and so that saidprepit on another of said recording tracks adjacent to said one of saidrecording tracks is covered with said long mark or long space.
 15. Amethod for recording data on the optical recording medium according toclaim 3, said method comprising the step of covering said prepit on oneof said recording tracks with said long mark or long space, andrecording a pattern including a long mark or a long space having ten ormore times said channel bit length on an area which is aligned with saidprepit forming region in said zone and includes therein no prepitforming region.
 16. A recording unit for recording data on the opticalrecording medium according to claim 1, said recording unit comprising: aprepit detecting section for detecting a prepit signal from a signalreproduced from the optical recording medium; a decoding section fordecoding said prepit signal to output physical address information; arecording pattern generating section for admixing, based on data to berecorded, a recording pattern including a long mark or a long spacehaving a length ten or more times said channel bit length to said datato be recorded, to generate physical address information; and arecording timing control section for detecting a recorded position basedon said physical address information, and controlling timing for startof a recording pattern output from said recording pattern generatingsection and a channel bit frequency, wherein said recording timingcontrol section controls output timing of said recording pattern so thatsaid long mark or said long space output from said recording patterngenerating section covers said prepit.
 17. A recording unit forrecording data on the optical recording medium according to claim 1,said recording unit comprising: a wobble detecting section for detectinga wobble phase from a signal reproduced from the optical recordingmedium; a prepit detecting section for detecting a prepit signal from asignal reproduced from said optical recording medium; a decoding sectionfor decoding said prepit signal to output physical address information;a recording pattern generating section for admixing, based on data to berecorded, a recording pattern including a long mark or a long spacehaving a length ten or more times said channel bit length to said datato be recorded, to generate physical address information; and arecording timing control section for detecting a recorded position basedon said physical address information, and controlling timing for startof a recording pattern output from said recording pattern generatingsection and a channel bit frequency, based on said wobble phase outputfrom said prepit detecting section and/or said prepit signal output fromsaid prepit detecting section, wherein said recording timing controlsection controls output timing of said recording pattern so that saidlong mark or said long space output from said recording patterngenerating section covers said prepit.